This project concerns a characterization of enzyme repression in bacteria, particularly in Escherichia coli. The emphasis will be on the biochemical mechanism underlying repression. The mode of repressor action, the site of repressor action, the nature of functional repressor, and repression-related enzymological phenomena are to be investigated. We propose to concentrate on the translational and transcriptional components of repression in the arginine biosynthetic system. The work is to include an examination of the stability of specific messenger RNA's of the arginine system, as a function of repression-derepression conditions. The specific messenger RNA's will be detected by DNA-RNA hybridization methods.